Characterizing non-covalent nucleic acid interactions with small molecules and proteins by calorimetry

The expression or replication of genes is affected by the binding of small molecule ligands and proteins to nucleic acid sequences. Such binding events are critical for the physiological integrity of organisms and therefore are of fundamental interest to life scientists. Recently, the thermodynamics driving these interactions have also become important to pharmaceutical scientists investigating the anticancer, antibacterial and antiviral potential of nucleic acid/ligand interactions. In addition, as the number of diseases identified as being due to a malfunction of cellular control processes increases, the possibility of treating disorders by manipulating gene expression is further focusing attention on the thermodynamics underlying nucleic acid binding affinity and specificity. Calorimetry is the most accurate and rapid approach for obtaining direct thermodynamic information which, in combination with high resolution structural data and mechanistic studies, provides the most complete picture possible of the factors involved in the recognition and binding of nucleic acids to ligands. This application note examines the utility of differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC) for characterizing the energetics governing nucleic acid/ligand complexes. For general descriptions of the principles behind DSC and ITC, please see TA’s overview notes entitled Life Science Applications of DSC and Life Science Applications of ITC.